All Reflections in Blender are Completely Black in look dev mode
I'm posting this only so I can post a screenshot. This is from my copy of blender (2.83) using the same settings you outlined. If all your settings are the identical, it's got to be some kind of bug or problem with your setup. See image:

EDIT - I downloaded your .blend file, changed nothing and took a screenshot. This is what I get - take is as you will: